The specific objectives of my research proposal are as follows: 1. Examine the role of the Na ion-ion gradient and membrane potential in the low affinity transport of GABA by neurons in culture. 2. Determine the location and density of binding sites for GABA on differentiating GABAergic neurons in vitro and vivo. 3. Define, characterize, and localize the externally oriented membrane proteins of granule cell and GABAergic neurons in cell culture. 4. Produce monoclonal antibodies to neuronal plasma membrane-associated antigens, and utilize these antibodies in the studies listed above. The methods to be used include cell culture and hybridization, iodination, gel electrophoresis, centrifugation, fluorometry, radioautography, fluorography, lectin binding, immunohistochemistry, and light and scanning electron microscopy.